The present invention relates to apparatus for producing ultraviolet radiation, especially for treatment of psoriasis and certain other skin diseases.
It is known to treat psoriasis and similar skin diseases by exposing the affected area of the skin to a narrow range (approximately 300-330 nm) of ultraviolet radiation, namely, to radiation in the upper portion of the so-called UVB range ("Dorno" region of 280 to 315 nm) and in the lower portion of the so-called UVA range ("near" region of 315 to 400 nm). The aforementioned spectral zone between approximately 300 and 330 nm includes radiation which contains sufficient amounts of quantum energy for the skin treatment and is capable of penetrating into the epidermis to reach the inner boundary of the epidermis, i.e., the stratum which is the staging point of psoriasis. The just discussed spectral zone is immediately adjacent to that portion of the UVB range which causes sunburn; therefore, the lower limit of the desirable spectral zone for treatment of psoriasis or related diseases must be selected and maintained with a high degree of accuracy. The quantum energy of radiation in the spectral region above approximately 330 nm is too low to exert any beneficial antipsoriatic effect.
A presently known apparatus for treatment of psoriasis employs a source of ultraviolet radiation which comprises a high-pressure metal vapor lamp whose contents are selected in such a way that the radiation includes several pronounced spectral lines in the region between 300 and 330 nm. The lamp is a point source of radiation and, therefore, such lamp cannot insure uniform irradiation of large areas, e.g., of the major part of or the entire body of a patient. Moreover, the emission of light and heat energy is so high that the source must be held at a considerable distance from the patient, i.e., the density of the radiation field in the region of the affected area is low so that the patient must be exposed to radiation for extended periods of time. Another drawback of conventional apparatus is that they also emit radiation in several narrow zones of the lower ultraviolet range of the spectrum.